Acoustic control system

ABSTRACT

A control system including an input device for providing a plurality of variable input signals. The input signals are combined in a multiplexer and transmitted acoustically through a sound pipe to a receiver. The signals are then separated and transmitted to one or more actuators or other devices for performing a control function.

iteoi States atent [191 Stevens Inventor:

Assignee:

F iled:

Appl. No.:

U.S. Cl.

Int. Cl. Field 340/15, 340/16 C, 181/.5 R G08b 13/16 of Search 340/15, 16 R, 18 NC, 340/18 LD; 333/30 R References Cited UNITED STATES PATENTS 10/1968 Koomey et a1 340/16 C 2/1941 Kellogg 333/30 R [451 Aug. 14, 1973 3,638,174 1/1972 Haase et a1. 340/16 C 2,751,577 6/1956 DuBois 340/15 Primary Examiner-Benjamin A. Borchelt Assistant Examiner-A. M. Psitos Attorney-Smyth, Reston & Pavitt [5 7] ABSTRACT A control system including an input device for providing a plurality of variable input signals. The input signals are combined in a multiplexer and transmitted acoustically through a sound pipe to a receiver. The signals are then separated and transmitted to one or more actuators or other devices for performing a contro] function.

15 Claims, 3 Drawing Figures /3a i f 7 (/5 l 9 51px MULTIPLEXEB TRANSMITTER l3c ,7 I r 45 1 V 4/) (oi/$032} DEMl/lT/PZEXER RELAY J colvmouee 43 Patented Aug. 14, 1973 3,753,221

- MULTIPLEXER TRANSMITTER g2/ 23 25 2/ MODULAT'IIV SIGNAL 6, I I I P q 2 z). MODULATED 7 ACCOUST/C CARR/EH SIGNAL I NUENTOB Curtis E. Steve/1s ACOUSTIC CONTROL SYSTEM BACKGROUND OF THE INVENTION Actuators such as hydraulic actuators are used to carry out many different control functions in response to input information. In many circumstances the actuators must be remotely located and this means that control signals must be transmitted to the remote actuator. Often there is a requirement for high voltage electrical insulation between the input device and remote actuators.

The control signals can be transmitted in a variety of ways including the use of radio frequency signals or optical transmission. The RF method is either very expensive or if made less expensive, it is not adequately reliable. In addition, RF signals are subject to jamming. The optical method is either unreliable due to interference or else dependent upon flexible light pipes or similar devices.

SUMMARY OF THE INVENTION The present invention provides a control system in which a control signal is transmitted acoustically. The acoustic signal is not as subject to jamming as an RF signal. The acoustic signal is preferably transmitted through a sound pipe which is, in effect, a sonic wave guide. The sound pipe can ,be a flexible tube with a hard, reflective, smooth inner surface. Such a pipe is superior to a flexible fiber optics system which is much more easily damaged. The maintenance and repair of a sound pipe are much easier than the maintenance and repair of a flexible fiber optics tube.

The acoustic signal can advantageously be transmitted through the sound pipe in the form of a modulated acoustic carrier signal. Because a carrier is used, the sound pipe can have apertures therein without significantly effecting the transmission capabilities of the sound pipe. An aperture in the wall of a sound pipe is advantageous for draining condensation from the interior of the pipe. In addition, an aperture may be created in the wall of a sound pipe as a result of a loose joint or connection between sound pipe sections. This will have a negligible effect on the transmission of the acoustic signal in accordance with the teachings of this invention. Another advantage of the acoustic sisgnal is that high frequencies, for example, of the order of 15-100 KC can be utilized with 30-50 being preferred. This frequency range is largely unused and therefore the likelihood of jamming is minimized.

The present invention is adapted to transmit multiplexed input signals. Each of the signals may be utilized to control a separate actuator or other device. The term actuator" is used in a broad sense to mean a de vice which moves something. One of the signals may be utilized to control a safety device which prevents operation of one or more of the actuators when predetermined conditions are sensed.

The acoustic signal may be transmitted through the sound pipe in a variety of different ways. Although different kinds of modulation may be utilized, amplitude modulation is preferred, because with frequency modulation standing waves may be produced in the pipe. For multiple control channels, a modulation method may be superimposed with time or frequency multiplexed signals. A preferred system is interrupted carrieramplitude modulation/pulse duration modulation (IC- /AM/PDM). This has the advantage of being simple in that it is basically a digital system. In addition, pulse duration modulation rejects noise.

For safety, the modulated acoustic carrier signal includes a relatively wide sychronizing band followed by a plurality of variable width bands which define signals, the duration of which varies in accordance with the intelligence being transmitted. One of these signals is a safety signal which operates a safety device. If the safety signal is of a predetermined duration, all of the acuators being controlled can function normally; however, if the safety signal is not of the predetermined duration or has a duration of zero for a few cycles, relays open to prevent the actuators from operating.

The invention can best be understood by reference to the following description taken in connection with the accompanying illustrative drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic view of a control system constructed in accordance with the teachings of this invention.

FIGS. 2a and 2b are plots of modulating signal and modulated acoustic carrier signals, respectively, versus time.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows a control system 11 constructed in accordance with the teachings of this invention. The control system 11 includes a plurality of input devices 13, including input devices 13a, 13b and 13, each of which is coupled to a multiplexer 15. Each of the input devices 13a, 13b and 13c provides a variable electrical input signal to the multiplexer 15. In the embodiment illustrated, each of the input devices 13a, 13b and 13c is a manual input device and has a manual control member 17 which is movable to provide a variable electrical input signal to the multiplexer 15 with the electrical input signal being varied in accordance with the position of the control member. It should be understood that the-input devices 13 may be operated automatically in response to various parameters such as those of the type which maybe obtainable from various sensing devices or in response to a computer program. Also, the input devices 13 can be integrated into a single unit in which event the three electrical input signals would be derived from the movement of the manual control member 17 along three different axes, respectively.

The multiplexer 15 is coupled to a transmitter 19. The multiplexer 15 combines the signals from the input devices 13 into an input modulating signal, a characteristic of which varies in accordance with each of the input signals from the input devices 13. The transmitter 19 generates an acoustic carrier signal and modulates the acoustic carrier signal in accordance with the input modulating signal from the multiplexer 15.

Although various methods of modulation can be employed, the illustrated embodiment of the present invention employs interrupted carrier-amplitude modulation-pulse duration modulation. With reference to FIG. 2a, the modulating signal from the multiplexer 15 includes a synchronizing band 21 followed successively by two narrower bands 23 and 25, another synchronizing band 21, etc. The modulating signal is interrupted between the bands 21, 23 and 25 as illustrated.

The transmitter 19 produces a carrier signal 27 which is modulated by the modulating signal. Thus, the carrier signal is totally interrupted during time periods x, y and 2 which are between times 11 and t2, t3 and t4, and t5 and 16, respectively. Thus, the modulating signal modulates the duration of the pulses of the carrier signal 27 except for the synchronizing band 21 which is of fixed duration. In this manner, each of the time periods x, y and z is an acoustic signal which is variable. Of course, the variable signals could be periods other than the periods x, y and z.

The modulated acoustic carrier signal (FIG. 2b) is transmitted through a sound pipe 29 to an acoustic receiver 31. The sound pipe 29 is in the form ofa flexible tube. Maximum transmission distance is obtained if the pipe has a hard, sound reflective, smooth inner surface 33. The sound pipe 29 may be an integral pipe, or it may be composed of two or more sections suitably interconnected. The sound pipe has an aperture 35 therein to permit water drainage out of the sound pipe as when condensation forms therein. Polyethylene has been found to be a good material for the sound pipe 29.

The receiver 31 provides an output modulating signal to a demultiplexer 37. The output modulating signal is substantially identical to the modulating signal shown in FIG. 2a. The receiver is tuned so that low frequency noises will not jam it and has a sufficiently broad band to handle the modulated acoustic carrier signal.

The control system 11 includes two output devices 39 and 41 and a relay controller 43. The output devices 39 and 41 may be identical, and accordingly, only the output device 39 is shown in any detail. Of course, any numbers of the input devices 13 and output devices 39 and 41 can be utilized, and the number of these devices shown in FIG. 1 is purely illustrative.

The demultiplexer 37 separates the signals combined by the multiplexer into three separate output signals for controlling the output devices 39 and 41 and the relay controller 43, respectively. In the embodiment illustrated, the demultiplexer 37 furnishes electrical signals to the output devices 39 and 41 which are a function of the duration of the signals x and y (FIG. 2b). The demultiplexer 37 provides an electrical output signal to the relay controller 43 which is a function of the duration of the signal z shown in FIG. 211. Thus, each of the signals provided by the input devices 13 performs a control function.

Although the output device 39 could take different forms, in the embodiment illustrated, it includes a motor controller 45 for controlling the speed and direction of rotation of a reversible electric motor 47. The motor controller 45 receives the electrical output signal from the demultiplexer 37 and conditions the signal. The motor controller 45 also includes the necessary servomechanisms which are responsive to the conditioned signal to control the speed and direction of rotation of the motor 47.

While the motor 47 is an actuator as that term is used herein, it drives a pump 49 which in turn controls a hydraulic actuator 51. Although the actuator 51 could take different forms, in the embodiment illustrated, it includes a cylinder 53, a piston 55 mounted for sliding movement in the cylinder and a connecting rod 57 mounted on the piston 55 for movement therewith. The piston 55 divides the cylinder into two chambers 59 and 61. The pump 49 supplies fluid to, and takes fluid from, the chambers 59 and 61 via conduits 63 and 65.

When the motor 47 is turned in a first direction to drive the pump 49 in a corresponding direction, bydraulic fluid is taken from the chamber 61 and supplied to the chamber 59 to thereby move the piston 59 upwardly as viewed in FIG. 1. The rate of movement of the piston 55 is controlled by the angular velocity of the motor 47. By reversing the direction of the motor 47 and the pump 49, fluid is withdrawn from the chamber 59 and supplied to the chamber 61 to thereby move the piston 55 downwardly as viewed in FIG. 1 with the velocity of piston movement being a function of the an gular velocity of the motor. The hydraulic portion of the output device 39 may include additional items such as a source of hydraulic fluid, relief valves, a mechanism to compensate for any unbalance in the actuator, etc.

The motor 47 receives its power from a suitable alternating current power supply 67. The circuit between the power supply 67 and the motor 47 includes a relay 69 which is operated by the relay controller 43. In the illustrated embodiment of the invention, the relay controller maintains the relay 67 in a closed position so long as the signal 2 (FIG. 2b) is within a predetermined narrow band and operates to open the relay 67 in response to the signal 2 being out of such band or being of zero duration for a few cycles. With the relay 69 open, the output device 39 including the actuator 51 is disabled. The output device 41 can be similarly disabled.

To start the system 11 the operator first moves the control member 17 of the input device 13a to the on position. This completes a circuit which powers the transmitter 19 and provides an electrical input signal from which the signal 2 (FIG. 2b) is derived. The control member 17 of the input device 13a may be spring biased to the off position so that if the operator becomes suddenly disabled, power to the transmitter 19 is cut and the rod 57 of the actuator 51 is thereafter held stationary. If, due to a malfunction, the transmitter 19 should continue transmitting, the movement of the off position gives the signal z a zero duration so that after a few cycles, the relay 69 is opened by the relay conroller 43 to terminate operation of the motor 47 and movement of the rod 57. Thus, redundant safety devices prevent operation of the system if the operator becomes stricken. As the control member 17 of the input device 13a operates in an on-off mode, in an actual construction this control member may take the form of a button on one of the control members 17 of the input devices 13b and 130.

In normal operation of the control system 11, the operator moves one or more of the manual control members 17 of the input devices 13b and 13c to thereby provide input information to the system. Each of the input devices 13b and whose manual control member 17 has been moved provides an electrical input signal to the multiplexer 15 which is a function of the position of the associated manual control member 17. The multiplexer 15 combines the input signals to form the modulating signal shown in FIG. 2a. The modulating signal is used by the transmitter 19 to modulate the carrier signal 27 to provide a modulated acoustic carrier signal (FIG. 2b). The duration of the signals at, y and z are variable depending upon the input from the input devices 13b, 13c and 13a, respectively.

The modulated acoustic carrier signal is transmitted through the sound pipe 29 to the receiver 31 which provides an output modulating signal to the demultiplexer 37. The demultiplexer 3'7 separates the signals of the output modulating signal and transmits each of the signals to the appropriate output device 39, 411 or to the relay controller 43. For example, if the signal x (FIG. 2b) is of greater duration than a reference value, the motor 47 rotates in one direction, and if the duration of the signal x is less than the reference period, the motor rotates in the opposite direction. The motor 47 is stopped when the duration of the signal x equals the duration of the reference period, and the velocity of the motor increases as the difference between the duration of the signal x and the duration of the reference period increase. The output device 41 is similarly controlled by the duration of the period y.

The synchronizing band 21 and the signal 2 make it virtually impossible for the system 1 1 to be operated or jammed by extraneous sounds. In order to operate the system it is necessary to have many cycles each of which includes a signal of the relatively long duration of the synchronizing band followed by two signals x and y of variable duration and the signal 2. If the signal 2 is not of a predetermined duration or has a duration of zero for a few successive cycles, the relay controller 43 opens the relay 69 and a corresponding relay in the output device 41 to thereby prevent further operation of the system. Obviously, it is virtually impossible to have enough cycles of these signals generated externally to operate the output devices 39 and 411.

Although an exemplary embodiment of the invention has been shown and described, many changes, modifications and substitutions may be made by one having ordinary skill in the art without necessarily departing from the spirit and scope of this invention.

I claim:

I. A control system conrising:

first means for providing a plurality of variable electrical input signals;

multiplexer means coupled to said first means for providing an input modulating signal which is related to said variable electrical input signal; transmitter means for generating an acoustic carrier signal and modulating said acoustic carrier signal in accordance with said input modulating signal;

a receiver;

conduit means for conducting the modulated acoustic carrier signal to said receiver;

said receiver including means for providing an output modulating signal which is related to the modulated acoustic carrier signal;

demultiplexer means for providing a plurality of electrical output signals related to said output modulating signal;

an actuator; and

second means responsive to at least one of said electrical output signals for operating said actuator.

2. A control system as defined in claim 1 wherein said conduit means has at least one aperture in the wall thereof.

3. A control system as defined in claim ll wherein a second of said electrical output signals is capable of having a predetermined characteristic, said control system including means responsive to said predetermined characteristic for preventing operation of said actuator.

4. A control system as defined in claim 1 wherein said actuator is a first actuator, said control system includes a second actuator and third means responsive to another of said electrical output signals for operating said second actuator.

5. A control system as defined in claim 1 wherein said acoustic signal includes a plurality of acoustic pulses and said input modulating signal selectively interrupts said acoustic pulses.

6. A control system as defined in claim 1 wherein said second means includes an electric motor, said conrol system including safety means responsive to a second of said output signals for interrupting the supply of current to said motor to prevent operation of the actuator.

7. A control system as defined in claim l wherein said output signals include a second output signal and a third output signal, said third output signal having a predetermined characteristic, said first means includes manual means for providing input information from which said variable electrical input signals are derived, said actuator is a first actuator, said control system including a second actuator, third means responsive to a second of the electrical output signals for operating said second actuator, and means responsive to said predetermined characteristic for preventing the operation of at least one of said actuators.

8. A conrol system as defined in claim 7 wherein said acoustic signal includes a plurality of acoustic pulses and said input modulating signal selectively interrupts said acoustic pulses.

9. A control system as defined in claim 8 wherein said first actuator includes a housing and a piston movable in said housing and dividing said housing into first and second chambers, said second means including a reversible motor and a pump driven by said motor to pump fluid between said chambers whereby said piston is moved in a first direction as said reversible motor rotates in one direction and said piston is moved in a second direction as the motor rotates in the other direction thereof, said one electrical output signal controlling the direction of rotation of said motor.

10. A control system comprising:

an input device for providing variable input information;

first means responsive to the input information for producing an input signal, a characteristic of the input signal being variable in accordance with the variations in the input information;

transmitter means responsive to said characteristic of the input signal for producing an acoustic signal, a characterisic of the acoustic signal being variable in accordance with variations in said characteristic of the input signal;

a receiver;

a sound pipe for conducting the acoustic signal from the transmitter to the receiver; said receiver including means for producing an electrical output signal, a characteristic of the electrical output signal being variable in accordance with variations in said characteristic of the acoustic signal;

an actuator; second means responsive to said characteristic of the output signal for controlling the actuator; and

said acoustic signal including a plurality of acoustic pulses, said pulses being arranged in a plurality of groups with the acoustic pulses being interrupted between said groups.

11. A control system as defined in claim 1 wherein the variable characteristic of said acoustic signal is the interval between adjacent pulses.

12. A control system comprising:

an input device for providing variable input information;

first means responsive to the input information for producing an input signal, a characteristic of the input signal being variable in accordance with the variations in the input information;

transmitter means responsive to said characteristic of the input signal for producing an acoustic signal, a charcterisic of the acoustic signal being variable in accordance with variations in said characteristic of the input signal;

a receiver;

a sound pipe for conducting the acoustic signal from the transmitter to the receiver; said receiver including means for producing an electrical output signal, a characteristic of the electrical output signal being variable in accordance with variations in said characteristic of the acoustic signal;

an actuator; second means responsive to said characteristic of the output signal for controlling the actuator; and

safety means responsive to a predetermined condition of said acoustic signal for preventing operation of said actuator.

13. A control system comprising:

an input device for providing variable input information;

first means responsive to the input information for producing an input signal, a characteristic of the input signal being variable in accordance with the variations in the input information;

transmitter means responsive to said characteristic of the input signal for producing an acoustic signal, a characteristic of the acoustic signal being variable in accordance with variations in said characteristic of the input signal;

a receiver;

a sound pipe for conducting the acoustic signal from the transmitter to the receiver; said receiver including means for producing an electrical output signal, a characteristic of the electrical output signal being variable in accordance with variations in said characteristic of the acoustic signal;

an actuator; second means responsive to said characteristic of the output signal for controlling the actuator; and

said actuator including a movable member, said second means including a reversible motor and means for moving the movable member of the actuator in first and second directions in response to rotation of the reversible motor in first and second directions, respectively, the direction of rotation of said motor being controlled by said variable characteristic.

14. A control system as defined in claim 13 wherein said means for moving the movable member includes a pump driven by said reversible motor, said actuator including first and second fluid receiving chambers and said pump pumping fluid from the first chamber to the second chamber and from the second chamber to the first chamber when said motor is driven in said first and second directions, respectively, to thereby move the movable member in the first and second directions, respectively.

15. A control system as defined in claim 14 wherein the variable characteristic of said acoustic signal is the interval between adjacent pulses and including safety means responsive to a predetermined condition of said acoustic signal for preventing operation of said actua- 

1. A control system conrising: first means for providing a plurality of variable electrical input signals; multiplexer means coupled to said first means for providing an input modulating signal which is related to said variable electrical input signal; transmitter means for generating an acoustic carrier signal and modulating said acoustic carrier signal in accordance with said input modulating signal; a receiver; conduit means for conducting the modulated acoustic carrier signal to said receiver; said receiver including means for providing an output modulating signal which is related to the modulated acoustic carrier signal; demultiplexer means for providing a plurality of electrical output signals related to said output modulating signal; an actuator; and second means responsive to at least one of said electrical output signals for operating said actuator.
 2. A control system as defined in claim 1 wherein said conduit means has at least one aperture in the wall thereof.
 3. A control system as defined in claim 1 wherein a second of said electrical output signals is capable of having a predetermined characteristic, said control system including means responsive to said predetermined characteristic for preventing operation of said actuator.
 4. A control system as defined in claim 1 wherein said actuator is a first actuator, said control system includes a second actuator and third means responsive to another of said electrical output signals for operating said second actuator.
 5. A control system as defined in claim 1 wherein said acoustic signal includes a plurality of acoustic pulses and said input modulating signal selectively interrupts said acoustic pulses.
 6. A control system as defined in claim 1 wherein said second means includes an electric motor, said conrol system including safety means responsive to a second of said output signals for interrupting the supply of current to said motor to prevent operation of the actuator.
 7. A control system as defined in claim 1 wherein said output signals include a second output signal and a third output signal, said third output signal having a predetermined characteristic, said first means includes manual means for providing input information from which said variable electrical input signals are derived, said actuator is a first actuator, said control system including a second actuator, third means responsive to a second of the electrical output signals for operating said second actuator, and means responsive to said predetermined characteristic for preventing the operation of at least one of said actuators.
 8. A conrol system as defined in claim 7 wherein said acoustic signal includes a plurality of acoustic pulses and said input modulating signal selectively interrupts said acoustic pulses.
 9. A control system as defined in claim 8 wherein said first actuator includes a housing and a piston movable in said housing and dividing said housing into first and second chambers, said second means including a reversible motor and a pump driven by said motor to pump fluid between said chambers whereby said piston is moved in a first direction as said reversible motor rotates in one direction and said piston is moved in a second direction as the motor rotates in the other direction thereof, said one electrical output signAl controlling the direction of rotation of said motor.
 10. A control system comprising: an input device for providing variable input information; first means responsive to the input information for producing an input signal, a characteristic of the input signal being variable in accordance with the variations in the input information; transmitter means responsive to said characteristic of the input signal for producing an acoustic signal, a characterisic of the acoustic signal being variable in accordance with variations in said characteristic of the input signal; a receiver; a sound pipe for conducting the acoustic signal from the transmitter to the receiver; said receiver including means for producing an electrical output signal, a characteristic of the electrical output signal being variable in accordance with variations in said characteristic of the acoustic signal; an actuator; second means responsive to said characteristic of the output signal for controlling the actuator; and said acoustic signal including a plurality of acoustic pulses, said pulses being arranged in a plurality of groups with the acoustic pulses being interrupted between said groups.
 11. A control system as defined in claim 1 wherein the variable characteristic of said acoustic signal is the interval between adjacent pulses.
 12. A control system comprising: an input device for providing variable input information; first means responsive to the input information for producing an input signal, a characteristic of the input signal being variable in accordance with the variations in the input information; transmitter means responsive to said characteristic of the input signal for producing an acoustic signal, a charcterisic of the acoustic signal being variable in accordance with variations in said characteristic of the input signal; a receiver; a sound pipe for conducting the acoustic signal from the transmitter to the receiver; said receiver including means for producing an electrical output signal, a characteristic of the electrical output signal being variable in accordance with variations in said characteristic of the acoustic signal; an actuator; second means responsive to said characteristic of the output signal for controlling the actuator; and safety means responsive to a predetermined condition of said acoustic signal for preventing operation of said actuator.
 13. A control system comprising: an input device for providing variable input information; first means responsive to the input information for producing an input signal, a characteristic of the input signal being variable in accordance with the variations in the input information; transmitter means responsive to said characteristic of the input signal for producing an acoustic signal, a characteristic of the acoustic signal being variable in accordance with variations in said characteristic of the input signal; a receiver; a sound pipe for conducting the acoustic signal from the transmitter to the receiver; said receiver including means for producing an electrical output signal, a characteristic of the electrical output signal being variable in accordance with variations in said characteristic of the acoustic signal; an actuator; second means responsive to said characteristic of the output signal for controlling the actuator; and said actuator including a movable member, said second means including a reversible motor and means for moving the movable member of the actuator in first and second directions in response to rotation of the reversible motor in first and second directions, respectively, the direction of rotation of said motor being controlled by said variable characteristic.
 14. A control system as defined in claim 13 wherein said means for moving the movable member includes a pump driven by said reversible motor, said actuator including first and second fluid receiving chambErs and said pump pumping fluid from the first chamber to the second chamber and from the second chamber to the first chamber when said motor is driven in said first and second directions, respectively, to thereby move the movable member in the first and second directions, respectively.
 15. A control system as defined in claim 14 wherein the variable characteristic of said acoustic signal is the interval between adjacent pulses and including safety means responsive to a predetermined condition of said acoustic signal for preventing operation of said actuator. 